Space Based Solar Power Reading Answers

In an energy-hungry world, new safe ways to generate electricity are constantly being sought.
Space-based solar power, or SBSP, is not yet up and running, but several space agencies and commercial companies are keenly pursuing it.
SBSP is a system that would harness sunlight in space, convert it into electrical energy, and beam this to receivers in the Earth's equatorial zone. SBSP satellites would be in low orbit 1100 kilometers (684 miles) above the Earth.

Advantages

To date, solar energy has been collected on the ground, but it is estimated there is 144% more solar power available in space as the Earth's atmosphere absorbs light. Furthermore, since our planet rotates, energy can only be collected during daylight. It is possible at the poles to collect light almost continuously in summer, but in winter such plants cannot operate due to snow, ice, and darkness. In space, however, solar power collection could occur around the clock. A further benefit may be that the energy produced could be directed to multiple locations whereas terrestrial power plants are limited to sending power one way into a grid.

Design

Most prototypes of SBSP structures look like a giant tent hanging in space. It's light, hollow equilateral triangular frame is 336 meters (1103 feet) long while its depth is 303 meters (994 feet).

Down two sides are solar collectors, called arrays; on the floor of the 'tent' sit a solar converter and a transmitting antenna. The antenna sends microwaves to Earth. These waves are at a frequency of 2.45-5.8 gigahertz, or somewhere between infrared and radio signals. They pass through Earth's atmosphere easily with only minor energy loss. On Earth, the invisible column of microwave energy - perhaps two to three kilometers (a mile or two) wide - is received by a large oval-shaped rectenna' - a new word combining 'rectifying' + 'antenna'. A pilot beam, also on Earth, ensures the satellite stays in position in space.

Two major technical obstacles remain before SBSP becomes a reality. The first is launching satellites into orbit. While most scientists favor low orbit, others believe a higher orbit like 36,050 kilometers (22,400 miles), about one-tenth of the distance between Earth and the Moon, would harness more sunlight. However, no agency or company has any experience of launching and controlling a satellite in high orbit, and the cost would be exorbitant. The second problem is the wireless power transmission. While this seemed like a physicist's fantasy a few years ago, in 2009, US and Japanese researchers successfully sent microwave energy between two islands in Hawaii which are 145 km (90 miles) apart equidistant to Earth's atmosphere - but it is unknown whether this can be reproduced in space.

History

SBSP is not a new idea. Dr Peter Glaser designed a system in the late 1960s and was granted a US patent in 1973. The US Department of Energy in conjunction with NASA (the American space agency) conducted feasibility studies in the 1970s, but a conservative administration in the 1980s discontinued investment. Only in 1997 did the US government reconsider the idea.

In 2009, an American commercial company Space Energy Incorporated announced it planned to provide SBSP 'within a decade'. Subsequently, a company called Solaren stated it was likely to provide 200 megawatts of solar power from an SBSP to Pacific Gas and Electric from 2016. PowerSat Corporation has begun the process of patenting a system of interconnected satellites that will project one extremely powerful microwave beam down to Earth. It has also developed a special thruster to lift a satellite from low orbit into a higher orbit.

Small-scale scientific projects connected to SBSP have long been in operation in Europe. In 2010, several private European firms joined the space power race, and scientific conferences were held on electromagnetic wireless transmission in Italy and Germany.

Japanese initiatives

It is the Japanese, however, who have come nearest to producing a reliable system. Both Mitsubishi Electric Corporation and IHI Corporation currently fund research. Since 1998, JAXA (the Japanese space agency) has been involved in all aspects of SBSP, and it predicts its first satellite will be in orbit by 2030.

There are six broad areas that JAXA is working on. These are (1) general configuration; (2) assembly work and operation; (3) solar array; (4) transmitting antenna; (5) power transmission and reception system; and, (6) testing methods. The first of these is the most developed. The solar array and transmitting antenna are second in terms of development. Testing methods are relatively unsolved. Assembly work and operation, and power transmission and reception system remain far from being solved.

Disadvantages

SBSP has numerous detractors. There are those people who imagine the microwave beam to be something like a science-fiction death ray. Physicists reassure the public it is a non-ionising wave, like a radio wave or x-ray. It cannot displace electrons from atoms to charge particles, so it does not damage DNA. The waves may be slightly warm, but they present (o danger to wildlife or humans.

Other opponents of SBSP say that while there is neither corrosion nor damage from plants or animals in space, background radiation could harm the satellite. There is the very real danger of collision with space junk as recently happened at the International Space Station, or with small meteors' hitting it. The less likely event of an enemy nation firing rockets to destroy the equipment also causes concern. Repairing an unmanned structure so far from Earth would be extremely difficult.

Solar power via the Moon is an option which some scientists say can be in operation in ten years at a fraction of the cost.

But the majority of those against SBSP consider it expensive and unnecessary given that many other forms of renewable energy on Earth are operating successfully. Terrestrial solar power is relatively underdeveloped; the Arizona Desert in the US, and deserts across North Africa provide easily-accessible locations for new systems that would be five times more cost-effective than SBSP

Viability

Nevertheless, as energy requirements accelerate, as unrest in oil- producing regions and nuclear accidents make alternative energy more attractive, space-based solar power may have the future after all.